On the relation between the Mason number and the durability of MR fluids

Abstract

The durability of magnetorheological (MR) fluid is a fundamental aspect of any MR device, as MR fluid is submitted to shear stresses that cause its degradation. While various studies have identified MR fluid degradation behaviors and proposed improvements, there exists no generalized failure theory to help understand the in-use degradation of MR fluids. In this regard, this study suggests that a relation exists between the Mason number and the maximum achievable lifetime dissipated energy (LDE) of MR fluids. To validate this hypothesis, custom (perfluoropolyether) and commercial (hydrocarbon) MR fluids are aged in various Mason number conditions using a clutch-type durability device. Experimental results show that under a critical Mason number of ∼1, LDE of the MR fluids can be related to the Mason Number using an analogy to metal fatigue failure. Above this critical Mason number, the fundamental degradation mechanism appears to change from a dominant mechanical wear of the particles (i.e. particle-limited) to another mechanism (i.e. fluid-limited) which is not yet fully understood. Since MR generally operate well below the critical Mason number of ∼1, the relation between the Mason number and the particle-limited regime durability of MR fluids can be very useful to design novel MR fluids or MR devices, as it provides a way to estimate the impact of various design strategies on the total expected life of the device.

Investigation of shear-induced physical and chemical transformations of Fe microparticles in hydrocarbon- and fluorocarbon-based magnetorheological fluids

“…The production of visible spalling residue in the form of nanoparticles suggests more abrasive conditions associated with the low Mn runs. These observations are in line with the lower LDE observed at low mason number [22]. This observation is consistent with the findings of [13,15] who argue that MR fluids will form easier-to-disperse, small particle clusters at higher Mn.…”

Magnetorheology: a review

“…In the post-yield regime, the degradation mechanism is not clear but seems to be related to thermal/ chemical effects in the carrier fluid. 54 For a recent review on the shortcomings of MR technology we refer to Wahid et al 55…”

An optical red green blue sensor for monitoring the degradation of magnetorheological fluids in flow-recirculating high-torque clutch actuators

“…Three tests were made with a PFPE, based homemade fluid using a commercial oil known as Krytox GPL-103 to investigate the effect of fluid formulation on sensor performance. This fluid has been selected because it has showed sufficient lifetime capabilities for flight control applications in previous works (>10 MJ/mL) (Lucking Bigué et al, 2019). The test conditions are summarized in Table 3 and were selected to represent varying conditions of torque, rotational speed (r/min), and dissipated power.…”